DE60036432T2 - Cell search method, communication synchronizer, and portable terminal - Google Patents

Description

The The present invention relates to a cell search method, a communication synchronization device, a portable terminal device and a program (stored on a recording medium can) for realizing the method and the device. In particular, the present invention may be used, for example be a synchronization between a mobile communication terminal, such as a portable phone, and a base station.

Conventionally in analog FDMA (Frequency Division Multiple Access) for connecting mobile stations such as portable telephones with one Base station using different frequencies a frequency band exclusively for used the communication of a mobile station. This lowers the usage efficiency the divided frequency bands and it also makes it impossible the number of users in the service area (cell) of the base station to increase.

Currently becomes common Digital Time Division Multiple Access (TDMA) TDMA (Time Division Multiple Access) for one time shared connection of a frequency band with mobile stations instead used by the FDMA. Because according to this Scheme two or more mobile stations a frequency band for communication can be assigned For example, the number of users can be increased compared to the FDMA.

There however TDMA segmented signals are time divided between the base station and the mobile stations are exchanged, the amount of information becomes the communication of a mobile station low. To the amount of information to increase communication Send current portable digital phones and the like. Signals passing through a coding be compressed. On the receiver side, the signal is expanded and reproduced. For this reason, the quality is reproduced Speech lowered.

In In recent years, the Code Division Multiple Access (CDMA) has which uses a direct spread spectrum as a communication scheme size Attention found that the efficiency of use of each frequency band strong increase and can also reproduce high quality speech.

At the CDMA are sent from a base station to mobile stations Signals using for the respective mobile stations spread spreading code unique and sent using a frequency band. A mobile station on the receiver side multiplies received signals by the specific spreading code, which is associated with the mobile station to provide a correlation between this and any spread code used on the transmitter side. The mobile station thereby detects the correlation maximum value, and only extracts a signal addressed to the mobile station. According to the CDMA can be a frequency band of a larger number be assigned by mobile stations using different spreading codes. In addition, since the amount of information to be sent can be increased the quality reproduced Language to be improved.

When a mobile station, such as a portable telephone, is turned on, it must receive a predetermined message from the base station in the area (cell). In the CDMA, the message from the base station is repeatedly transmitted in units of predetermined slots, as in 1 shown. The mobile station is not always turned on at the start time setting of one slot and can not read the message correctly when it is turned on at another time, as indicated by an arrow in 1 displayed.

Around must correctly decode the message contained in the slot the start timing of the slot can be detected (this is called "cell search"), and the Message must be received from this time setting. A Cell search is not for the initial cell search described above Trapping of the cell is limited at the time of turning on the Mobile station is to connect. More specific may be, even after switching on, for example when the mobile station moves over cells, move the synchronization. Therefore, a synchronization shift becomes always monitored by periodically performing a cell search.

2 Fig. 10 is a block diagram showing the construction of a cell search circuit of the conventional wideband CDMA (CDMA direct spreading) communication scheme provided in a mobile station. With reference to 2 are used for a received signal (transmission channel signal, as in 1 shown transmitted from a base station (not shown)) the first 1-bit data of each slot indicated by a hatched portion in FIG 1 are spread by a common spreading code (a spreading code which changes 256 times in one bit: number of chips = 256) which is created independently of the spreading codes unique to the respective mobile stations. Normally, such a transmission channel signal for cell search is transmitted using a common channel (perch channel).

An in-phase component I and a quadrature component Q of the voltage of such Receiving signal are through an A / D converter 101 converted to digital signals and sequentially to a correlator 102 , such as a matched filter or a sliding correlator, in units of slots (one slot corresponds to 10 symbols) supplied to the mobile station from the power-on time setting. The correlator 102 integrates each of the A / D converter 101 input digital signal with the mobile stations common spreading code, that of a code generator 103 is generated so as to make a despreading.

The in-phase component I and the quadrature component Q of the voltage resulting from the correlator 102 are output to an energy conversion section 104 and converted into energy values in units of predetermined sampling points in the slot. The energy values obtained at the sampling points are sequentially addressed to addresses of a memory (RAM) 107 corresponding to the respective sampling points by an adder 106 in an energy value integration section 105 saved.

In the above process, only the portion having a high correlation with the common spreading code which is multiplexed by the mobile station in the first slot after turning on the mobile station, that is, only the energy value of the hatched portion in FIG 1 wherein the common spreading code is multiplied by the base station (not shown) as a maximum. Therefore, when this maximum portion is detected, the start position of the slot can be confirmed, and subsequent communication can be made in accordance with this timing.

In fact, a mobile station receives transmission channel signals with delays from two or more base stations close to the mobile station, as in FIG 1 shown. In addition, signals from a base station include not only direct waves received directly from the base station but also waves reflected from buildings or the ground and then received. For this reason, a received transmission channel signal, in a slot, has a number of sections spread by the common code, and a number of maximum power values are detected in a slot. In this case, when the mobile station is moving in the cell search mode, the maximum in the next slot may be detected at a position other than the previous position.

In view of these situations, the maximum energy value is detected not only for the first slot after turning on the mobile station, but over some slots. More specifically, the energy integration values up to the previous slot become the RAM 107 in units of sample points and the adder 106 fed. The energy values at the same sample point in the current slot are added together and again in the RAM 107 saved. By integrating the energy values over a few slots, the section with the largest maximum is finally recognized as the starting section of the transmission channel signal transmitted by the nearest base station.

The number of times of integrating the energy values (slot count) is stored in an integration count setting register 108 set. A counter 109 increments the count by one every time the integration of one slot is completed. When the count value is one in the integration count setting register 108 set value is reached, the counter indicates 109 a timing signal and the integration is terminated.

However, when performing cell search using the above conventional method, the RAM is needed 107 for storing the energy integration value at each sampling point, the capacity of 10,240 words. That is, the number of chips (the number of cycles) in a slot of the perch channel for cell search is 256 × 10 = 2,560. To increase the accuracy of the maximum value detection, a chip is divided into four divisions and an oversampling of 4 times is performed. Therefore, the total number of sample points in a slot is 10,240 (when the chip rate is 4 Mcps).

The area of RAM 107 to store 10,240 words of energy integration values is a few square mm or more. This causes a very large circuit area. Especially for a portable communication terminal such as a portable telephone, it is important to make it compact and lightweight. Circuits for transmission, reception and cell search functions must be stored in one chip. However, since the area of the cell search circuit becomes very large on the LSI, the LSI itself can not be made compact.

Because data with the largest value out of those in the RAM 107 In addition, when the stored 10,240 energy integration values have been stored, the processing load is high and it takes a long time to complete the cell search. For example, a long time is required for an initial cell search at power-on, and the start-up time until the communication is released becomes very long.

In the cell search using the above conventional method, the number of Making the integration of energy values considering a bad receiving sensitivity state set relatively large (eg for 32 slots) so that a path can be extracted with the maximum even if the signal receiving sensitivity is low. For this reason, the time required for the cell search is constant regardless of the signal reception state. Even if the receiving state is good, the integration is made a number of times more than necessary, and it takes a long time to complete the cell search.

The US-5 530 716-A discloses a method and apparatus according to the preamble of each respective independent claim. In this method and apparatus, the correlation values (correlation energies) are accumulated and summed with the respective correlation energies obtained at respective offsets to produce the total correlation energies in multiple search windows (ie multiple translations via the energy control group, or in other words, via a slot of a CDMA frame). In a preferred embodiment, only the set of correlation energies reaching or exceeding a predetermined threshold is used to determine the total correlation energies. The total correlation energy in a search window corresponding to an offset is determined, for example, by summing the correlation energies obtained at that offset via the power control group (slot) and which meet or exceed the threshold level.

It It is an object of the present invention to increase the capacity of cell search used RAM to compact the cell search circuit and to increase the speed of cell search operation.

A Another object of the present invention is the cell search time in accordance shorten with the signal reception state.

It is still another object of the present invention, the circuit area of RAM for A cell search is used to reduce to a more compact realize mobile communication terminal.

According to the present Invention will be a cell search method, a synchronization device and a computer program as defined in the independent claims.

So will only exceed the threshold Correlation value stored in a memory. In addition, time settings data can be added to the time when the correlation value exceeds the threshold, in a memory at the same time as storing the correlation value get saved.

at of the present invention are obtained from those obtained in a slot Correlation values, the correlation values that exceed the threshold, stored in the memory, and the correlation values representing the Do not exceed threshold are neglected as noise data. The unnecessary Correlation values on noise levels are not stored in the memory saved. For this reason, compared with the state of Technique in which all detected correlation values in a memory stored, the number of actually stored in the memory Correlation values are reduced.

Therefore can greatly reduce the necessary storage capacity of the memory and so can the physical circuit area of the memory significantly be reduced. additionally Can the burden in the process of finding the greatest value reduced among the correlation values stored in the memory and so can the correlation maximum value at a higher speed be detected. In a portable telephone e.g. of the wideband CDMA scheme can be a Cell search at high speed and size reduction the circuit for it will be realized.

Now a detailed description is given by way of mere examples with reference to the accompanying drawings, in which:

1 is a diagram for illustrating a cell search operation;

2 Fig. 10 is a block diagram showing the construction of a conventional cell search circuit;

3 Fig. 12 is a block diagram showing the construction of a cell search circuit according to a first embodiment of the present invention;

4 Fig. 12 is a block diagram showing an example of a construction for realizing a cell search method according to the first embodiment using software;

5 Fig. 10 is a flowchart of the cell search method according to the first embodiment;

6 Fig. 10 is a block diagram showing the construction of a cell search circuit not in accordance with the present invention;

7 a block diagram is an example of a Construction for realizing a cell search method according to the construction of 6 using software;

8th a flow chart of a cell search method according to the construction of 6 is that is executed in an integration release mode;

9 Fig. 10 is a block diagram showing the construction of a cell search circuit not according to the present invention; and

10 is a block diagram illustrating the construction of a correlator according to the circuit of 9 shows.

3 Fig. 10 is a block diagram showing the construction of a cell search circuit according to an embodiment of the present invention.

An in 3 shown received signal (external input signal) is a as in 1 shown transmission channel signal which is transmitted from a base station (not shown). The first bit of each slot, indicated by a hatched section in 1 is displayed is spread by a spreading code (number of chips = 256), which all mobile stations have in common. An inphase component I and a quadrature component Q of the voltage of this received signal are limited to the frequency band of the signal transmitted from the base station through a band pass filter (not shown) and an A / D converter 1 is supplied.

The A / D converter 1 converts the above-described received signal into a digital signal. A correlator 2 sequentially calculates the integration between the A / D converter 1 input digital signals and the mobile stations common spreading code generated by a code generator 3 is generated in units of slots from the ON-time setting of a mobile station to perform despreading so as to detect the correlation between the mobile station's own spreading code and the received signal. The correlator 2 For example, it is constructed from a matched filter or sliding correlator.

An energy conversion section 4 calculates the sum of squares of the in-phase component I and the quadrature component Q of one of the correlation 2 output voltage for each of 10,240 sample points set in advance in a slot to obtain a correlation energy value. An energy value integration section 5 integrated, in units of sampling points, from the energy conversion section 4 output energy value at each sample point for some slots.

The A / D converter 1 , the correlator 2 , the code generator 3 and the energy conversion section 4 are the same as the conventional A / D converter 101 , the correlator 102 , the code generator 103 and the energy conversion section 104 , in the 2 are shown. The energy value integration section 5 is a characteristic feature of the present invention. The energy value integration section 5 will be described in detail below.

In a threshold checking section 11 compares a comparator 13 from the energy conversion section 4 output energy value with a predetermined energy threshold 12 in units of sample points. The active / negative state of a pass signal is controlled in accordance with the relationship in the order of magnitude between the given energy value and the threshold value. An energy value memory (RAM) 14 saves that from the comparator 13 output energy value in the threshold checking section 11 , A multiplexer 15 selects and reads one of the energy values at the sample points that are to addresses in the energy value store 14 are stored, and supplies the energy value to an input terminal of an AND gate 16 to.

A carry propagation adder 17 adds the from the AND gate 16 output data value with that from the comparator 13 output energy value in the threshold checking section 11 and stores the result in the energy value memory 14 , For example, if an energy integration value to the previous slot at a given sample point derived from the energy value store 14 through the multiplexer 15 is read through the AND gate 16 passes, the energy integration value with the energy value at the same sampling point in the current slot by the carry propagation adder 17 and the sum is stored in the energy value store 14 stored at the same address.

If "0" data from the AND gate 16 by a mask signal (to be described later), the energy value goes to a certain sampling point in the current slot that is from the comparator 13 in the threshold checking section 11 is output directly through the carry propagation adder 17 through and is at a new address in the energy store 14 saved.

A score memory (RAM) 18 stores the value of the sample point corresponding to that in the energy value store 14 stored energy value, ie timing information, such as the relative time (relative cycle count) from the slot head in a slot, that of a timer 23 measured in units of slots. One multiplexer 19 selects and reads one of the sample point values that are sent to addresses in the point value memory 18 are stored, and pass the sample point value to an input terminal of a comparator 20 to.

Relative time information (the current sample point value in the current slot) from the slot header provided by the timer 23 are measured in the other input terminal of the comparator 20 entered. The comparator 20 compares the current sample point value with the sample point value obtained from the dot value store 18 through the multiplexer 19 is read out, and supplies a signal representing whether both values coincide with each other to a pointer control section 21 to.

The pointer control section 21 controls the pointer (address) of read / write data in the energy value store 14 and the score memory 18 in accordance with a pass signal from the comparator 13 in the threshold checking section 11 is fed, and the coincidence / incoincidence signal from the comparator 20 is supplied. If an incoincidence signal from the comparator 20 is supplied, the pointer control section performs 21 the other input terminal of the AND gate 16 a mask signal too. In this case, go out of the comparator 13 output energy value directly through the carry propagation adder 17 through and is at a new address in the energy store 14 stored as described above.

A register group 22 provides various functions for the cell search operation of this embodiment. Details thereof will be described below. The timer 23 counts the relative time (relative cycle count) from the slot head in a slot in units of slots. In this embodiment, the counting operation is started, for example, at the start of reception by turning on the mobile station. When the count reaches 10.239, it is reset to 0.

The following is the operation of the energy value integration section 5 described with the above construction. First, the operation for the first slot immediately after turning on the mobile station will be described. The energy value at each sample point coming out of the energy conversion section 4 is output, with the predetermined energy threshold 12 in the threshold checking section 11 compared. If the energy value is greater than the threshold (or greater than or equal to the threshold), the pass signal becomes active. If the energy value is less than or equal to the threshold (or less than the threshold), the pass signal remains negative.

Only when the pass signal is active are the energy values obtained at that time in the energy value memory 14 by the carry propagation adder 17 stored sequentially from an upper address. Simultaneous with the storage of energy values become sample point values which correspond to energy values greater than the energy threshold 12 in the point value memory 18 stored sequentially from the top address. The two memories 14 and 18 sequentially store energy values greater than the energy threshold 12 , and sample point values corresponding to the energy values are sequentially sent to identical addresses.

In the first slot for integration, energy values greater than the energy threshold will become 12 , and sample point values corresponding to the energy values in the two memories 14 and 18 necessarily registered. For the second and subsequent slots, the threshold comparison is the same as in the first slot. The operation that is done when the energy value is the energy threshold 12 but differs from that for the first slot. If the energy value is the energy threshold 12 does not exceed, and the pass signal remains negative, no process is performed at that sampling point, as in the first slot.

For the second and subsequent slots, if the energy value is the energy threshold 12 exceeds, a search using the multiplexer 19 and comparator 20 to check whether the sample value corresponding to the energy value is already in the dot value memory 18 was saved. If it turns out that the sample point value by the processing of the previous slot already in the point value memory 18 was stored, the pointer control section performs 21 such control by that the energy value integration section 5 operated as follows.

From the energy integration values to the previous slot in the energy value memory 14 are stored, an energy integration value at an address that is equal to that at the point value memory 18 is identical, where the sampling point is stored, by the multiplexer 15 and the carry propagate adder 17 through the AND gate 16 fed. The carry propagation adder 17 adds the read energy integration value from the previous slot to that from the comparator 13 supplied current energy value. The sum result will be at the same address in the energy value store 14 saved.

For the second and subsequent slots, if the energy value is the energy thresholds value 12 and the sample corresponding to the energy value does not exceed the dot value memory 18 was registered by the processing of the previous slot, the new sample point value at a new address in the dot value memory 18 saved. In addition, a mask signal is output from the pointer control section 21 issued to the from the comparator 13 output energy value at a new address in the energy value memory 14 by the carry propagation adder 17 save.

When such energy value integration processing is performed for some slots, the integration result becomes energy values larger than the energy threshold value 12 , and sample point values corresponding to those in the energy value memory 14 stored energy integration values, in the energy value memory 14 and the score memory 18 stored sequentially from the upper addresses by the processing in each slot. Then select a DSP (digital signal processor) 25 , the one with the energy value integration section 5 through a data bus 24 , the largest energy integration value of at least one in the energy value memory 14 stored energy integration value. This makes it possible to recognize that the sampling point value corresponding to the energy integration value corresponds to the slot head portion of the transmission channel signal transmitted from the nearest base station.

According to the cell search scheme of this embodiment as described above, the energy threshold value becomes 12 set in advance. When data values converted to energy values using a spreading code are to be stored in the memory (RAM), only data values exceeding the threshold are stored, and data values smaller than or equal to the threshold value are not stored. Since unnecessary data values of a noise level are not stored in the memory, the number of words necessary as storage capacity of the memory can be made much smaller than those of the prior art.

For example, to detect 20 waves of integrated relative energy values in descending order, the memory requires a capacity equal to at least 20 words. Although it is assumed that about 80 waves (= 20 waves × 4 multipath) of energy maximum values are detected in one slot assuming direct waves and reflected waves from the nearest base station, waves from another base station, or other interference waves must be received by a mobile station, the energy value memory 14 and the score memory 18 have only memory capacities that correspond at least to the number of words. In the in 3 As shown, each memory has a memory capacity of 128 words with a certain margin. The storage capacity is much smaller than the conventional storage capacity of 10,240 words.

There in this embodiment the number of words the as storage capacity a RAM are needed, can be greatly reduced, as described above, can the circuit area of RAM are made much smaller than in the prior art.

In addition will be in search processing for data having the largest value among stored in the RAM Energy integrates the data from a maximum of 128 energy integration values selected. Because of this, the processing load can be reduced and the maximum energy maximum can be at a higher speed be detected.

Next is the in 3 shown register group 22 described. An energy threshold register 31 is used to the energy threshold 12 arbitrarily set by the comparator 13 in the threshold checking section 11 is to be compared. A threshold value of the user's choice can be freely selected by the contents in the energy threshold register 31 be rewritten. For example, when a portable terminal having the cell search circuit of this embodiment is used in a city where the building density is high, the number of maxima in one slot is expected to increase. In this case, an overflow of memory can be prevented by setting a high energy threshold 12 is set. When the energy threshold 12 is made larger or smaller in accordance with the registration situation of the correlation energy value in the first slot, despreading can be performed in accordance with the wave receiving state.

An integration time register 32 is used to set the energy value integration time in the cell search, ie the number of slots to be integrated. An integration time after the user's choice can be freely selected by the contents of the integration time register 32 be rewritten. For example, in a city where the building density is high, it is expected that the number of maxima in a slot will increase. In this case, an accurate cell search can be performed by setting a large number of slots to be integrated. If the portable terminal is used in a rural area, where a smaller number of reflected waves and Interference waves is present, a cell search can be performed at high speed by a small number of slots is set.

A control register 33 is used to start the cell search operation or the pointers of the memory 14 and 18 to zero to interrupt the cell search operation. More specific is the tax register 33 an area where a start bit is prepared. When "1" is written in this area, the cell search operation starts. The relative time in a slot is from the timer 23 counted from this start time. The tax register 33 has another area where a reset bit is prepared. If "1" is written in this area, only the pointers become the memory 14 and 18 set to zero. The tax register 33 is designed to test for abnormal operations prior to delivery of a product.

A time information register 34 is used to in the point value memory 18 stored time information (sample point value) on the data bus 24 read. If this time information register 34 are read, the more specific in the point value memory 18 stored time information is sequentially read by being incremented by one, and by the data bus 24 output.

The time information register 34 is used, for example, by the cell search mode, the maximum value among those in the energy value memory 14 stored energy integration values, and to detect a sampling point value corresponding to the maximum energy integration value. The time information register 34 can also be used to store all the time information in the score memory 18 to verify the number of maxima at a given time during testing prior to delivery of the products.

An energy integration value register 35 is used to store in the energy store 14 stored energy integration value on the data bus 24 as a result of the cell search. If this energy integration value register 35 is read, the more specific in the energy value memory 14 stored energy integration value is sequentially read out by being incremented by one and by the data bus 24 output. The energy integration value register 35 is used, for example, by the cell search mode, the maximum value among those in the energy value memory 14 to detect stored energy integration values.

A status register 36 is used to, through the data bus 24 , the DSP 25 to report whether the cell search operation is completed or the energy value memory 14 and the score memory 18 have overflowed during the cell search operation, because too many energy values the energy threshold 12 exceed. A user may monitor the state of the cell search operation by having a display section (not shown) view the contents of the status register 36 indicating what the DSP 25 is reported. If this status register 36 For example, when testing before delivery of the products, the default value of the energy threshold may be used 12 or the number of words used as the storage capacity of each of the energy value memories 14 and the score memory 18 be verified.

A registration count register 37 is used to the DSP 25 the number of words corresponding to the energy integration values and sample point values corresponding to the energy integration values stored in the energy storage 14 or point value memory 18 stored as a result of a cell search. For example, based on the contents of the status register 36 it is confirmed that the cell search is completed next to the contents of the registration count register 37 Referenced to determine the number of words actually registered. In this case, the maximum maximum value may be detected by energy integration values corresponding to at least the number of words from the energy integration value register 35 can be read out, and the cell search processing time can be shortened.

The cell search method of this embodiment as described above is represented by the in 3 realized circuit construction realized. However, it can also be realized by the operation of a program stored in the RAM or ROM of a computer. 4 FIG. 13 is a block diagram illustrating a construction example for implementing the invention with reference to FIG 3 described cell search method in software. The same reference numbers as in 3 denote the same blocks in 4 ,

With reference to 4 is a ROM 41 a read only memory storing a program for executing a cell search operation of this embodiment and various necessary data. A RAM 42 is a random access memory for temporarily storing a variety of data obtained in the process of a cell search operation based on the program, or for storing data finally obtained by the cell search. The RAM 42 contains the energy value store 14 and the score memory 18 , in the 3 are shown. The RAM 42 can save the program.

An operation section 43 is used by the user to perform operations necessary for voice communication using a portable terminal or desired values in the registers 31 to 37 to be discontinued in the in 3 shown register group 22 are provided. A display section 44 shows a variety of set contents in the register group 22 or various messages.

The DSP (CPU) 25 which serves as the control section mainly performs the operations of the correlator 2 , the energy conversion section 4 and the energy value integration section 5 through, in 3 or a process of detecting the maximum value among those in the RAM 42 stored energy integration values by the cell search to the slot head portion in accordance with that in the ROM 41 or the RAM 42 to find saved program. In this case, the DSP takes 25 also the operations of the correlator 2 and the energy conversion section 4 in front. The correlator 2 and the energy conversion section 4 however, they can work independently of the DSP 25 be provided to perform the operations.

An I / F section 45 takes a process of receiving a signal received from a receiving section (not shown) or transmitting various signals to a transmission section (not shown). The I / F section 45 is also used to load the program with which the DSP 25 works to provide the cell search function. The program for realizing the cell search method of this embodiment is stored on, for example, a recording medium such as a CD-ROM and the RAM 42 or a hard disk (not shown) through the I / F section 45 fed. As the recording medium to which the program is supplied, not only a CD-ROM but also a floppy disk, a hard disk, a magnetic tape, an optical magnetic disk or a non-volatile memory card can be used.

5 Fig. 10 is a flowchart for explaining the operation of performing a cell search by software processing.

If with reference to 5 the reception of a transmission channel signal from the base station is started in step S1, the timer becomes 23 for counting the relative time (relative cycle count) from the slot head in each slot in step S2, and the flow proceeds to step S3.

In step S3, it is determined whether the integration is completed, that is, whether the integration is made for a predetermined number of slots. If YES in step S3, the cell search operation is ended. If slots are still left, the flow proceeds to step S4 to determine whether the count for a slot by the timer 23 finished. If YES in step S4, the timer becomes 23 reset in step S5, and the flow proceeds to step S6. If NO in step SS4, the flow proceeds to step S6 without processing.

In Step S6 becomes, for a current sample point to be processed, a correlation between the Spread code of the mobile station and the received signal detected, and at the same time, the detected correlation value becomes an energy value converted. In step S7, it is determined whether the energy value converted correlation value (correlation energy value) is greater as a predetermined threshold. If YES in step S7, goes the flow proceeds to step S8 to further determine whether the currently just integrated slot the first slot after launch the reception is.

If YES in step S8, the flow proceeds to step S11 to return the correlation energy value obtained in step S6 to a new address in the RAM 42 (the one in 3 shown energy value memory 14 corresponds to), and also to the appropriate piece of time information, by the timer 23 is counted (relative time from the slot header) to a new address in the RAM 42 (the one in 3 shown point value memory 18 corresponds) to write. The sampling point is incremented by one in step S12. Then, the flow returns to step S3 to perform the same process as described above for the next sampling point.

If the currently-integrated slot is not the first slot, ie, the second or a subsequent slot, the flow advances from step S8 to S9 to determine whether the same time information as that of the current sample point already exists in the RAM 42 (Score memory 18 ) were saved. If YES in step S9, the flow proceeds to step S10 to read out the energy integration value corresponding to the time information (sampling point value) from the RAM 42 equivalent. The obtained energy value is added to the energy integration value to perform integration. The result of integration is at the same address in the RAM 42 saved.

If NO in step S10, the flow proceeds to step S11 to return the newly obtained correlation energy value to a new address in the RAM 42 (Energy-only memory 14 ) and corresponding time information to a new address in the RAM 42 (Score memory 18 ) to write. If the processing in step S10 or S11 is ended, the sampling point is incremented by one in step S12, and the flow returns to step S3 to perform the same process as described above for the next sampling point.

The operation that is performed when the correlation energy value at a particular sampling point is greater than the predetermined threshold has been described above. If it is determined in step S7 that the correlation energy value is less than or equal to the threshold value, the flow returns to step S3 via step S12, without processing in steps S8 to S11, and processing for the next sampling point is made. In this embodiment, only when the obtained correlation energy value is larger than the threshold, it becomes in the RAM 42 saved. Otherwise, the correlation energy value does not become in the RAM 42 saved.

With this construction, the storage capacity of the RAM 42 are greatly reduced compared with the prior art, and the circuit area of the RAM 42 can be made very small. For processing by the DSP 25 to get to the maximum value below that in the RAM 42 To search stored energy integration values, the processing load can be reduced, and the cell search operation can be performed at a higher speed.

In the first embodiment, two pieces of voltage information, ie the in-phase component I and the quadrature component Q, are generated by the correlator 2 are determined, converted to an energy value, and the correlation value converted to the energy value is integrated. However, the integration operation may be performed for each of the two correlation values, ie, the in-phase component I and the quadrature component Q. In this case, two threshold values are prepared for the in-phase component I and the quadrature component Q, respectively.

Around Energy values for to incorporate some slots are in the first embodiment Energy values that exceed the threshold are stored in the memory saved. When the transmission channel signal from the base station using a higher one Energy is sent, the slot head can only by detecting of the energy maximum detected in the area of the first slot and no integration is required. When a greater energy value as the threshold is detected, and a larger value remains, have to the energy values are therefore not saved.

In the in 3 embodiment shown are the energy value memory 14 and the score memory 18 provided separately. However, both the correlation energy value and the time information corresponding to the energy value may be stored in a RAM. For example, when a correlation energy value and time information corresponding to the energy value are stored in a word, the pointer control by the pointer control section 21 be simplified.

In the in 3 The embodiment shown, the output signal from the multiplexer 15 and the mask signal into the input terminals of the AND gate 16 entered. The mask signal is output when from the comparator 20 the pointer control section 21 an incoincidence signal is supplied. The output signal from the comparator 13 and the mask signal, however, may be input to the AND gate 16 can be input, and the mask signal can be output when the pass signal is negative (when the detected correlation energy value is the energy threshold value 12 does not exceed).

In this case, when the obtained correlation energy value does not exceed the threshold value and the pass signal is negative, the output signal from the multiplexer becomes 15 and "0" data from the AND gate 16 into the carry propagate adder 17 entered. For this reason, those in the energy value memory 14 stored contents are kept unchanged. When the obtained correlation energy value exceeds the threshold value and the pass signal is active, the output from the comparator 13 outputted correlation energy value into an input port of the carry propagation adder 17 through the AND gate 16 entered.

If an existing energy integration value from the energy value store 14 to the other input terminal of the carry propagation adder 17 through the multiplexer 15 is read out, at this time the value is added to the obtained correlation energy value obtained from the comparator 13 is output and stored at the same address. On the other hand, if the correlation energy value at the same sampling point is not stored by the processing in the previous slot, and a new address is designated as the area where the correlation energy value is to be stored, it becomes the one from the comparator 13 outputted correlation energy value directly at a new address in the energy value memory 14 by the carry propagation adder 17 saved.

In the in 5 In the illustrated embodiment, it is determined in step S8 whether the current slot is the first slot or the second or a subsequent slot, and the processing branches into Dependence on the result of determination. Even if the same process as that for the second and subsequent slots is made for the first slot, the same result is obtained. For this reason, the processing in step S8 is not always necessary.

Now An alternative cell search circuit will be described which does not according to the present invention is.

6 Figure 13 is a block diagram showing the construction of this cell search circuit. The same reference numbers as in

3 denote the same blocks in 6 ,

The in-phase component I and the quadrature component Q of the voltage of an in 1 The received signal transmitted from a base station (not shown) is limited to the frequency band of the signal transmitted from the base station through a band pass filter (not shown) and an A / D converter 1 is supplied.

The A / D converter 1 converts the above-described received signal into a digital signal. A correlator 2 sequentially calculates the integration between the A / D converter 1 input digital signals, and the spreading code common to the mobile stations received from a code generator 3 is generated in units of slots from the ON-time setting of a mobile station to perform despreading, so that the correlation between the spreading code of the mobile station and the received signal is detected.

An energy conversion section 4 calculates the sum-of-squares of the in-phase component I and the quadrature component Q of the voltage resulting from the correlator 2 for each of the 10,240 sample points set in advance in a slot to obtain the correlation energy value. An energy value integration section 5 ' integrated, in units of sampling points, from the energy conversion section 4 output energy value at each sample point for some slots.

The energy value integration section 5 ' has a RAM 7 for storing energy integration values (integration correlation values) in the previous slot, and an adder 6 for adding the energy integration values to the previous slot in the RAM 7 and the energy values in the current slot received by the energy conversion section 4 be supplied at the corresponding sampling points. Energy values are calculated using the adder 6 and the RAM 7 integrated. The RAM 7 This circuit stores not only an energy integration value for each of the 10,240 sample points, but also a control signal (to be described later) in units of sample points.

An integration count setting register 8th is used to set the number of times (the number of slots) of the integration of energy values in the normal integration mode (to be described later). A first counter 9 counts the number of times the integration of energy values. Each time integration for a slot is completed, the count is incremented by one. When the count value is the one in the integration count setting register 8th reached the set count, a time-out signal is output.

An integration limit setting register 51 is used to set the energy threshold value (corresponding to the reference setting value in the present invention) to be compared with the energy values integrated in units of sampling points. The energy threshold is set to a value that is necessary and sufficient to detect the maximum among the integrated energy values at the sample point.

An integration limit count setting register 52 is used to set a path count threshold (corresponding to the path count setpoint in the present invention) to be compared to the number of paths where the calculated energy integration value has reached the energy threshold. In recognizing the head portion of a slot, smaller values are those in the RAM 7 stored 10,240 energy integration values unnecessary. Therefore, a value necessary and sufficient for a slot header detection processing is set as a path threshold.

A mode register 53 is used to selectively select one of the normal integration mode, which is the same as the conventional integration scheme, and an integration release mode, which is unique to this circuit.

A comparator 54 compares, in units of sample points, from the adder 6 output energy integration value in the energy value integration section 5 ' with the advance in the integration limit setting register 51 set energy threshold. If the energy integration value is greater than the energy threshold, a path detection signal is output. A second counter 55 counts the number of paths where the energy integration value has reached the energy threshold. The count value is incremented by one each time a path detection signal from the comparator 54 is supplied. When the count value in advance in the integration limit count setting register 52 set number of paths, a time-out signal is output.

A circuit 56 will be in accordance with one from the RAM 7 opened / closed control signal read in units of sampling points so as to prevent a path once from the second counter 55 is counted, is counted again. In the initial state before the start of the integration is the circuit circuit 56 closed, and the output from the adder 6 becomes the comparator 54 fed. If the energy integration value calculated for each slot does not reach the energy threshold, the control signal will be at a position corresponding to the sample point in RAM 7 corresponds, held in the initial state, and the circuit circuit 56 is closed accordingly.

When, after a few slots from the start of integrating the energy integration value calculated at a given sampling point (path), the energy threshold reaches, the state of a control signal in the RAM becomes 7 at a position corresponding to the detected path in accordance with the state of the comparator 54 changed path detection signal changed. Even if, in the processing of subsequent slots, the energy integration value of the path (the energy integration value exceeds the energy threshold value) from the adder 6 is output, the circuit becomes 56 opened in accordance with a corresponding control signal to prevent the output energy integration value from the comparator 54 is supplied. This prevents the same path from being repeated by the second counter 55 is counted.

An AND circuit 57 calculates the AND between the integration cancellation mode setting signal and the time out signal from the second counter 55 is output, and outputs the result to an OR circuit 59 out. The other AND circuit 57 calculates the AND between the normal integration mode set signal and the time out signal from the first counter 9 and outputs the result to the OR circuit 59 out. The OR circuit 59 calculates the OR of the outputs of the AND circuits 57 and 58 and outputs the result as an end-of-integration signal.

When the normal integration mode is set, and the timing signal from the first counter 9 as a result of the integration performed a predetermined number of times, more specifically, an end-of-integration signal is produced by the AND circuit 58 and the OR circuit 59 and the integration operation is terminated. If the integration release mode was set, the timing signal becomes the second counter 55 as a result, the number of paths where the energy integration value has reached the energy threshold has reached the predetermined number of paths. The integration end signal is passed through the AND circuit 57 and the OR circuit 59 accordingly, and the integration operation is canceled.

The operation of the cell search circuit having the above construction will be described below. First, an operation in which the integration operation is not canceled will be described. In this case, the normal integration mode becomes the mode register 53 set.

When the cell search operation is started, the correlator detects 2 the correlation between the own spreading code of the mobile station and the received signal. The detected correlation value is from the energy conversion section 4 converted into an energy value. The one from the energy conversion section 4 Energy value output is from the Energy Value Integration section 5 ' repeatedly integrates a number of times, the one in advance in the integration count setting register 8th set number of slots corresponds. As a result, the energy integration values become sample points in the RAM 7 saved.

The ones in the RAM 7 stored energy integration values become the DSP 25 output. The DSP 25 selects the largest energy integration value from the energy integration values at the sample points stored in the RAM 7 are stored. With this operation, the position of the sampling point corresponding to the energy integration value can be recognized as a slot head portion of the transmission channel signal transmitted from the nearest base station.

Next, an operation in which the integration operation is interrupted will be described. In this case, the integration release mode becomes in the mode register 53 set. When this integration cancellation mode is set, the value in the integration count setting register becomes 8th set value is neglected.

When the cell search operation is started, the correlator detects 2 the correlation between the own spreading code of the mobile station and the received signal. The detected correlation value is from the energy conversion section 4 converted into an energy value. The one from the energy conversion section 4 Energy value output is from the Energy Value Integration section 5 ' integrated for a slot. The integrated energy values at sampling points are determined by the switching circuit 56 in the comparator 54 entered so that in the integration limit setting register 51 Energy threshold value is compared with the energy integration values in units of sampling points.

If there is a sample point at which of the energy value integration section 5 ' calculated energy integration value is greater than that in the integration limit setting register 51 set energy threshold, becomes a path detection signal from the comparator 54 output, and the count of the second counter 55 is incremented by one. It determines if the value of the second counter 55 in the integration limit count setting register 52 set number of paths has reached. If the count has not reached the number of paths, the integration operation continues.

Thereafter, the integration processing is performed in units of slots. If the count of the second counter 55 in the integration limit count setting register 52 set number of paths in a particular slot, the integration operation is stopped at that time. When the integration operation is completed, the DSP selects 25 the largest energy integration value from the energy integration values at the sample points stored in the RAM 7 are stored. With this operation, the position of the sampling point corresponding to the energy integration value is recognized as the slot head portion of the transmission channel signal transmitted from the nearest base station.

According to the cell search scheme of 6 As described above, the energy threshold and the path count threshold are set in advance. In the slit integration processing, it is determined whether the number of paths where the energy integration value has reached the energy threshold has reached the predetermined path count threshold. When the number of paths has reached the threshold, the integration operation on that slot is stopped. In this case, when the signal reception sensitivity is high, the energy integration value quickly reaches the energy threshold value, and the necessary number of paths is also quickly established. For this reason, the integration time can be shortened, the cell search operation can be performed at a higher speed, and the power consumption can be reduced.

The contents of the integration limit setting register 51 , the integration limit count setting register 52 and the mode register 53 can be arbitrarily set. For example, the threshold value can be freely selected by the user by changing the contents of the setting registers 51 and 52 be rewritten. The mode can also be freely selected by the user by changing the contents of the mode register 53 be rewritten.

The thresholds in the integration limit setting register 51 and the integration limit count setting register 52 can be done automatically by firmware like the DSP 25 be changed. For example, the quality of received speech is from the DSP 25 and the setting of the thresholds may be changed in accordance with the monitored quality of the received voice. If the received voice quality is poor, integration can continue with this design until a larger number of paths are detected.

In a city where the building density is high, for example, it is expected that the number of maxima increases in a slot. In this case, an accurate cell search accomplished be a big one Pfadzählwert threshold is set. If the portable terminal in a rural Area is used where a smaller number of reflected Waves and interference waves is present, can use a cell search high speed running by adding a small path count threshold is set.

The contents of the integration limit setting register 51 , the integration limit count setting register 52 and the mode register 53 can arbitrarily through an external terminal 10 be set. When different thresholds, for example, through the external terminal 10 during testing prior to delivery of the products, the default values of the thresholds that are in the integration limit set register can be verified 51 and the integration limit count setting register 52 are to be adjusted.

The cell search method as described above is different from the one described in 6 realized circuit design realized. However, it can also be realized by operating a program stored in the RAM or ROM of a computer. 7 is a block diagram showing an example of construction for the realization of with reference to 6 be described cell search method by software shows. The same reference numbers as in 6 and 4 denote the same blocks in 7 ,

With reference to 7 is a ROM 41 a read-only memory which stores a program for executing the cell search operation described above and various necessary data. The RAM 7 is a random access memory for temporarily storing a variety of data stored in the process of a cell search operation based on the Pro or to store data that will eventually be obtained by the cell search. The RAM 7 can save the program.

A register group 60 contains various registers such as the integration count setting register 8th , the integration limit setting register 51 , the integration limit count setting register 52 and the mode register 53 , in the 6 are shown. An operation section 43 is used by the user to perform operations necessary for voice communication using the portable terminal or desired values in the various registers 51 to 53 to set in 6 are shown. A display section 44 shows set contents in the different registers 51 to 53 or various messages.

The DSP (CPU) 25 mainly performs the operations of 6 or the process for detecting the maximum value under in the RAM 7 stored energy integration values using a cell search to match the slot head portion in accordance with that in the ROM 41 or the RAM 7 to find saved program. The DSP 25 Also takes the above-described process of monitoring the quality of received speech and rewriting the contents of the registers 51 and 52 in accordance with the monitoring result. In this case, the DSP takes 25 also the operations of the correlator 2 and the energy conversion section 4 in front. The correlator 2 and the energy conversion section 4 however, they can work independently of the DSP 25 be provided and carry out the operations.

An I / F section 45 takes the process of receiving a signal received from a receiving section (not shown) or transmitting a variety of signals to a transmission section (not shown). The I / F section 45 is also used to load the program with which the DSP 25 works to provide the cell search function. The program for realizing the above-described cell search method is stored on, for example, a recording medium such as a CD-ROM and the RAM 7 or a hard disk (not shown) through the I / F section 45 fed. As the recording medium to which the program is supplied, not only a CD-ROM but also a floppy disk, a hard disk, a magnetic tape, an optical magnetic disk or a non-volatile memory card can be used.

8th Fig. 10 is a flowchart for explaining how the cell search in the integration release mode is executed by software processing.

If with reference to 8th the reception of a transmission channel signal from the base station is started in step S21, a correlation between the own spreading code of the mobile station and the received signal is detected for a sampling point being processed, and in step S22 the correlation value is converted to an energy value. At the same time, the energy value is added with an energy integration value calculated for the same sample point in the previous slot.

In Step S23 determines whether the sample point being processed is already counted as a sampling point at which the calculated Energy integration value the energy threshold set in advance has reached. If YES in step S23, the flow goes to the step Continue to the next S27 Sample point to process. The sample point value is determined in step S27 is incremented by one, and the flow returns to step S22 to the same Process as described above for the next Make sample point.

If NO in step S23, the flow proceeds to step S24 to determine whether the energy integration value calculated in step S22 has reached the preset energy threshold. If the energy integration value is less than the energy threshold, the flow proceeds to step S27 to process the next sample point. The sample point value is incremented by one in step S27, and the flow returns to step S22 to the same process as described above for the next Make sample point.

If If YES in step S24, the flow advances to step S25 to get the Value of the counter to count increment the number of sample points (paths) at which the energy integration value has reached the energy threshold. In step S26, it is determined whether the count value at that time is in advance set path count threshold has reached.

If the counted Number of paths is less than the path count threshold goes the flow proceeds to step S27 to process the next sample point. In step S27, the sampling point value is incremented by one. Of the Flow returns to step S22, to perform the same process as described above for the next sample point. When the counted Number of paths reaches the path count threshold then the integration operation is terminated.

When the signal reception sensitivity is high, the integration processing is shortened with the above processing, and a cell search operation can be performed with high speed. The energy consumption can be reduced accordingly.

In the arrangement of 6 are two pieces of voltage information, ie the in-phase component I and the quadrature component Q, that of the correlator 2 are determined, converted to an energy value, and the correlation value converted to the energy value is integrated. However, the integration operation may be performed for each of the two correlation values, ie, the in-phase component I and the quadrature component Q. In this case, two threshold values to be compared with the integrated correlation value based on the voltage are prepared for the in-phase component I and the quadrature component Q, respectively.

In the arrangement of 6 becomes an energy integration value that is derived from the in 6 shown adder 6 is output, the comparator 54 fed. It may, however, be one out of RAM 7 read out energy integration value to the comparator 54 be supplied. Alternatively, one may be from the energy conversion section 4 output energy value to the comparator 54 be supplied. The latter can cope with a case where, when transmitting a transmission channel signal from the base station using high energy, the energy value calculated in units of slots can reach the energy threshold even without integration for some slots.

In the arrangement of 6 become an energy integration value and a control signal in the RAM 7 stored in units of sampling points. The circuit circle 56 will be in accordance with the from the RAM 7 read out control signal open / closed. However, the construction for preventing the same sampling point from being counted repeatedly is not limited to this example. For example, an AND circuit instead of the circuit circuit 56 be used. An energy integration value from the comparator 54 or the RAM 7 is input to one input terminal of the AND circuit, and a mask signal which becomes "0" for a counted sample point is input to the other input terminal.

Now Another alternative cell search circuit will be described which also not according to the present Invention is.

9 Fig. 10 is a block diagram showing the construction of this cell search circuit which is a communication synchronization apparatus included in a portable terminal device. The same reference numbers as in 3 and 6 denote the same blocks in 9 ,

The cell search circuit, as in 9 shown includes an A / D converter 1 , a correlator 61 , a code generator 3 , an energy conversion section 4 and an energy value integration section 62 , The correlator 61 and the energy value integration section 62 are characteristic features of this arrangement.

An in-phase component I and a quadrature component Q of the voltage of a voltage as in 1 The received signal transmitted from a base station (not shown) is limited to the frequency band of the signal transmitted from the base station through a band pass filter (not shown) and the A / D converter 1 is supplied.

The A / D converter 1 converts the above-described received signal into a digital signal. The correlator 61 inte grated sequentially from the A / D converter 1 input digital signals and the spread common to the mobile stations, the code generator 3 is generated, in units of slots from the ON-time setting of a mobile station, to perform despreading, so that the correlation between the spreading code of the mobile station and the received signal is detected. The correlator 61 For example, it is constructed from a matched filter or a sliding correlator.

The energy conversion section 4 calculates the sum-of-squares of the in-phase component I and the quadrature component Q of the voltage resulting from the correlator 61 for each of the 10,240 sample points set in advance in a slot to obtain the energy value.

The energy value integration section 62 integrated, in units of sampling points, from the energy conversion section 4 output energy value at each sample point for some slots. The energy value integration section 62 has a DRAM 64 for storing energy integration values (integration correlation values) in the previous slot, and an adder 63 for adding the energy integration values to the previous slot included in the DRAM 64 and the energy values in the current slot received by the energy conversion section 4 be supplied at the corresponding sampling points. Energy values are calculated using the adder 63 and the DRAM 64 integrated.

More specific are those from the energy conversion section 4 outputted correlation energy values in units of sampling points in one by the DRAM 64 constructed energy value memory stored sequentially from the start address. In this case, energy values at 10,240 sample points in a slot (625 μs) become sequential in the DRAM 64 saved with 10,240 words.

A maximum point will be the one in the DRAM 64 stored 10,240 correlation energy values are extracted to detect the slot head. The reliability is poor when data of only one slot is used, and the slot head can be erroneously determined. To prevent this, the correlation energy values at the 10,240 points are integrated for some slots to improve the reliability of data used to detect the correlation maximum.

The energy integration values up to the previous slot are from the DRAM 64 in units of sample points and the adder 63 fed. The energy values at the same sample point in the current slot are added together and in the DRAM 64 saved again. For example, energy values for 32 slots are integrated, and a section with the largest maximum is finally detected as the start position of the transmission channel signal transmitted from the nearest base station.

Now describes the characteristics of a DRAM. In a DRAM is a memory cell as an internal memory element by a Constructed capacitor. Because of this, disappearing into memory cells stored content, except the memory cells are each after a predetermined period Reloaded. The operation of charging the capacitors respectively after a predetermined period, refreshing is called, and the cycle is called a refresh cycle.

One Refresh-requiring DRAMs are conventionally called main memory or Expansion memory of a personal computer or workstation used. When a DRAM is used, it is specifically a control instruction for a Refresh additionally to memory cells required, and the control load is high. Faced with disadvantages in keeping data in memory cells used conventionally a compact mobile communication terminal like a portable phone no DRAM, but an SRAM that does not need a refresh operation.

However, when using a scheme of integration of energy values for some slots, as in the CDMA communication scheme, a refresh control can be omitted by data accessing (the process of reading out energy integration values up to the previous slot from the DRAM 64 adding these to the energy values in the current slot, that of the energy conversion section 4 supplied) and the writing of the values) instead of a refresh as a characteristic feature of the DRAM. Since the time of one slot is 625 μs and shorter than the refresh cycle, in fact, no refresh operation needs to be performed while the integration is being performed.

In the final cycle of integration, the maximum is detected while the addition by the adder 63 10,240 times, and the address of the DRAM 64 , which corresponds to the maximum point, is stored in a static memory (eg, an SRAM or a flip-flop that is in 1 not shown). After that, the integration results at the 10,240 points on the DRAM 64 disappear. Therefore, no refresh operation needs to be done even after the final cycle of integration.

In the circuit of 9 becomes the DRAM 64 as energy value store in the energy value integration section 62 used. The memory cells of the DRAM 64 As is known, they can have a much simpler structure than that of an SRAM. The DRAM 64 the circuit of 9 can also omit the on-fresh control design that is normally necessary.

Therefore can the circuit area of for the cell search used energy storage greatly reduced become. Also, in a portable terminal device of the broadband CDMA scheme, the one relatively large memory requires the data store with a size of about 1/4 that of a SRAM, conventionally known as Energy store is used.

Since the conventional FDMA or TDMA communication scheme does not require a large memory capacity, the circuit area rarely presents a problem even when an SRAM is used as internal memory. In contrast, the CDMA communication scheme requires a large memory capacity, and the circuit area becomes very large when an SRAM is used. The advantage obtained by using the internal memory using the DRAM 64 is formed is very big.

An example where the internal memory of the energy value integration section 62 from the DRAM 64 was formed, has been described above. Another data storage device used in a portable communication terminal that requires size reduction and data access with a shorter cycle than the refresh cycle may also be constructed using a DRAM. The correlator 61 For example, like a matched filter, for detecting a correlation between the input digital signal and the common spreading code may also use a DRAM as internal memory.

10 is a block diagram showing the construction of the correlator 61 shows that in the circuit of 9 is used. The correlator 61 has a correlator 71 with 16 taps, fifteen DRAMs # 1 72 to 15 74 , and two adders 75 and 76 , Although the correlator 61 to calculate the integration between the common spreading code and an input digital signal whose symbol has 256 chips can be constructed as a 256-tap correlator, this makes the correlator 61 large. One slot is spread by 256 chips entirely. More specifically, one slot has sixteen consecutive data values, each spread by sixteen chips. In this circuit, as in 10 The integration is done sixteen times using the correlator 71 with 16 taps, and the integration results are added and output.

The fifteen DRAMs 72 to 74 each store fifteen integration results sequentially from the correlator 71 with 16 taps for each of the inphase component I and the quadrature component Q. Each of the two adders 75 and 76 adds the first through the fifteenth integration results in the DRAMs 72 to 74 are stored with the sixteenth integration result that is currently from the correlator 71 is output with 16 taps, and output the sum result. The adder 75 adds results for the inphase component I of the voltage, and the adder 76 adds results for the quadrature component Q of the voltage.

In the circuit of 9 As described above, the internal memory of the energy value integration section is 62 from the DRAM 64 constructed, and additionally uses the correlator 61 also the DRAMs 72 to 74 as internal memory. The time of one slot is 625 μs as described above and is shorter than the refresh cycle. If the integration using the DRAMs 72 to 74 For this reason, the refresh operation need not be used. In the final cycle of integration can as well, after all integration values from the adders 75 and 76 are added and output, the integration results in the DRAMs 72 to 74 disappear. Therefore, even after the final cycle of integration, the refresh operation need not be performed.

Therefore, in this arrangement, the internal memory of the correlator 61 can also be realized with a very simple construction, and the circuit area of the memory used for the cell search can be further reduced.

In the circuit of 9 are two pieces of voltage information, ie, the in-phase component I and the quadrature component Q, that of the correlator 61 are determined, converted to an energy value, and the correlation value converted to the energy value is integrated. However, the integration operation may be performed for each of the two correlation values, ie the in-phase component I and the quadrature component Q.

In The above description has been particularly an initial cell search described when the portable terminal is turned on. The However, the present invention can also be applied to a cell search be done in a standby state.

The circuits of 6 and 9 may be arbitrarily combined with the embodiment of the present invention.

The Cell search scheme of the present invention can be used not only in mobile Communications using a portable telephone or the like and satellite communications, but also at digital TV.

The Construction and connection relationships between the sections in the circuits described above are mere examples of implementation the present invention, and the technical scope of the present Invention is not intended to be limited to the specific embodiment. This means, it can various changes and modifications are made without departing from the scope of the invention departing.

Claims (21)

A cell search method in which a station detects a correlation value between an input signal and a spreading code generated by the station itself, and detects a correlation maximum value in a predetermined unit of slots by the integration of the correlation value, wherein a threshold value ( 12 ) is provided to be compared with the detected correlation value such that a subject of the integration is limited, a correlation value exceeding the threshold value is made the subject of the integration, and stored in a memory ( 14 ), and a correlation value not exceeding the threshold value is excluded from the subject of the integration; characterized in that: the cell search method detects the correlation maximum value by an integration value that integrates the correlation value over a plurality of the slots, and that the correlation value not exceeding the threshold value is not stored in a memory; and that the method further includes: arbitrarily setting the threshold in a threshold register ( 31 ), and allow a user of the station to freely select the threshold by checking the contents of the threshold register ( 31 ), causing an overflow of memory ( 14 ) can be prevented. The method of claim 1, wherein timing data about the timing at which the correlation value exceeds the threshold is stored in a memory ( 18 ) get saved. Method according to Claim 2, in which, if the correlation value exceeds the threshold value ( 12 ) in the first slot of some slots after the start of the integration, the correlation value and the timing data corresponding to the correlation value are stored in a new area in the memory (FIG. 14 . 18 ) are necessarily saved. Method according to Claim 2 or 3, in which, if the correlation value exceeds the threshold value ( 12 ) in any of the second and subsequent slots of the some slots after the start of the integration, and the timing data about the timing at which the correlation value exceeds the threshold coincides with the timing data already stored in the memory, integration with the already in the memory ( 14 ) and the result is stored in the same area. Method according to one of Claims 2 to 4, in which, if the correlation value exceeds the threshold value ( 12 ) in any of the second and subsequent slots of the some slots after the start of the integration, and the timing data about the timing at which the correlation value exceeds the threshold does not match those already in the memory ( 14 . 18 ), the correlation value and the timing data corresponding to the correlation value coincide in a new area in the memory (FIG. 14 . 18 ) get saved. Method according to one of the preceding claims, in which the threshold value ( 12 ) can be arbitrarily set. Method according to one of claims 3, 4 or 5, in which the number of times of integration can be arbitrarily set. Synchronization device for use in a station for detecting a correlation value between an input signal and a spreading code generated by the station itself, comprising a device ( 2 ) for detecting a correlation maximum value in a predetermined unit of slots comprising an integration section ( 5 ) for integrating the correlation value to detect a synchronization point of the input signal, the integration section ( 5 ) comprises: a comparison section ( 13 ) for comparing the detected correlation value with a threshold value ( 12 ) to limit a subject of integration, and a first memory section ( 14 ), which integration section ( 5 ) is set up so that the threshold ( 12 ) is made the subject of the integration and in the first memory section ( 14 ), whereas a correlation value not exceeding the threshold value is excluded from the subject of the integration; characterized in that the integration section ( 5 ) is arranged to integrate the correlation value over a plurality of the slots, and is further arranged to set the threshold value ( 12 ) is not stored, and that the device further comprises: a threshold register ( 31 ) for storing the threshold, and means operable by a user of the station to select the threshold by adjusting the contents of the threshold register ( 31 ), causing an overflow of memory ( 14 ) can be avoided. Apparatus according to claim 8, further comprising a second memory section ( 18 ), which is set up, timing data about the time setting, at which the correlation value exceeds the threshold ( 12 ), and does not store timing data about the timing at which the correlation value does not exceed the threshold. Device according to Claim 9, in which the integration section ( 5 ) is operable so that: if the correlation value exceeds the threshold ( 12 ) in the first slot of some slots after the start of the integration, the correlation value and the timing data corresponding to the correlation value in the first and second memory sections ( 14 . 18 ), and if the correlation value is the threshold ( 12 ) in any one of the second and subsequent slots after the start of the integration exceeds, if the timing data on the timing at which the correlation value exceeds the threshold ( 12 ) coincide with the timing data already stored in the second memory section, the integration with that already in the first memory section ( 14 ) and the result in the first memory section ( 14 ) is stored. Apparatus according to claim 10, wherein the first and second memory sections ( 14 . 18 ) are set up so that when the correlation value exceeds the threshold ( 12 ) in any one of the second and subsequent slots after the start of the integration exceeds, if the timing data on the timing at which the correlation value exceeds the threshold ( 12 ), not with those already in the second memory section ( 18 ), the correlation value and the timing data corresponding to the correlation value in the first and second memory sections ( 14 . 18 ) get saved. Apparatus according to claim 10 or 11, wherein the first and second memory sections ( 14 . 18 ) are provided in a single memory. Device according to one of claims 8 to 12, further comprising a register ( 31 ) for arbitrarily setting the threshold. Device according to one of claims 8 to 13, further comprising a register ( 32 ) for arbitrarily setting the number of times of integration. Apparatus according to any of claims 8 to 14, further comprising an end message section (14). 36 ) for reporting the completion of the correlation maximum value detection process when the detection process is completed. Apparatus according to any of claims 10 to 15, further comprising an overflow message section (14). 36 ) for notifying a storage area shortage in at least one of the first and second storage sections ( 14 . 18 ) as it occurs. An apparatus according to any one of claims 8 to 16, further comprising a registration count message section (14). 37 ) for reporting the number of times in the first memory section ( 14 ) stored correlation values. Device according to one of claims 10 to 17, in which the integration over some slots are started after activation of the device. A computer program for a synchronization process performed in a station for detecting a correlation value between an input signal and a spreading code generated by the station itself, and detecting a correlation maximum value in a predetermined unit of slots by an integration value integrating the correlation value over a plurality of the slots by one Detect synchronization point of the input signal, the program causes the device, a comparison function of comparing the detected correlation value with a predetermined threshold ( 12 ) in such a way that a subject of the integration is limited, and a correlation value exceeding the threshold value is made the subject of the integration and stored in a memory ( 14 ), whereas a correlation value not exceeding the threshold value is excluded from the integration subject and is not stored in memory, which program further causes the device to perform the steps of: arbitrarily setting the threshold in a threshold register ( 31 ), and allow a user of the station to freely select the threshold by checking the contents of the threshold register ( 31 ), causing an overflow of memory ( 14 ) can be prevented. A program according to claim 19, further comprising causing the apparatus to perform a control function to store in a memory memory timing data about the timing at which the correlation value exceeds the threshold. 18 ) to control. Computer readable storage medium on which the program is stored according to claim 19 or 20.